The Swiss vote today on whether to restrict immigration, a step the government warns could undermine the economy.

Support for the initiative to “stop mass immigration,” which would impose an upper annual limit on newcomers, has risen, according to the most recent poll. While rejection still looks likely, high turnout among immigration opponents could tip the scales, pollster gfs.bern said.

Voting ends at noon local time and results are expected later in the day. Most Swiss will cast their ballots by mail.

“Support has been rising, though in general, initiatives tend to lose support as voting day approaches,” said Andreas Ladner, professor of public administration at the University of Lausanne. “Here the opposite is happening, and it’s possible it may pass.”

Swiss companies such as Basel-based drugmakers Roche Holding AG and Novartis AG, which rely on foreign professionals for lack of qualified local staff, stand to lose if the initiative passes. About 45 percent of employees in the country’s chemical, pharmaceutical and biotech industry are foreigners, according to scienceindstries, an association whose members include Roche, Nestle SA, the world’s biggest food company, and Clariant AG, a maker of specialty chemicals.

The government, which has already responded to immigration concerns by enacting a yearlong curb on residence permits for citizens from European Union countries including Germany and France, opposes the new limit. It “endangers prosperity,” Justice Minister Simonetta Sommaruga, said last month.

Open Doors

Switzerland opened its borders to EU workers nearly 12 years ago, while retaining a quota system for newcomers from countries such as Japan or the U.S.

Over the past decade, it has experienced the highest immigration relative to its population of any country in the Organization for Economic Cooperation and Development, said Thomas Liebig, an economist at the Paris-based organization’s international migration division. Italians are the biggest group of foreigners in the country of 8 million, followed by Germans, according to 2012 data.

Opponents of immigration -- many of them members of the Swiss People’s Party SVP -- say it’s causing a housing shortage, overcrowded public transport, a rising crime rate, and pressure to blue-collar wages.

Polarizing Matter

While immigration is a contentious topic in neighboring Italy, Austria and France, Switzerland stands apart because the anti-immigration vote targets some of the biggest economic contributors. Among arrivals from the EU between 2010 and 2012, 69 percent were highly skilled. That compares with a rate of 35 percent within the 28-member union, OECD data shows.

Another immigration initiative, which would cap the immigration rate at 0.2 percent of the resident population, is also in the pipeline. The government, which opposes that measure too, hasn’t yet set a voting date.

Skilled immigrants have played a prominent role in Swiss business for centuries. Geneva’s tradition of watchmaking traces its origins to the arrival of Huguenots in the 16th century, while in 1839 two Polish immigrants joined forces to form the company known today as Patek Philippe. Similarly, German immigrant Heinrich Nestle founded Nestle, the maker of Nespresso coffee, and Beirut-born Nicholas Hayek was the force behind Swatch Group AG.

Immigration helped national output exceed its pre-crisis level by 5 percent, according to the Swiss National Bank. Every year, it generates a gain of at least 6.5 billion Swiss francs ($7.2 billion) for the government, Liebig of the OECD said.

“We need these people,” says Marcel Sennhauser, head of communications at scienceindustries, the Zurich-based association. “There aren’t enough qualified Swiss people. If the initiative passes, it will be a bad sign for Switzerland as a workplace.”